Tagged: rtl2832u

Nigun (Melody): Open Hardware Plans for an RTL-SDR Downconverter

A downconverter is a circuit that allows the RTL-SDR to receive frequencies above its maximum frequency range of about 1.8 GHz. It works by converting all higher frequencies down into a lower frequency which can be received by the RTL-SDR. It is the opposite of an upconverter which is used to receive HF frequencies on an RTL-SDR. In the past the Outernet project was working on a commercial downconverter product for the RTL-SDR, but they had to unfortunately put an end to that project as the costs were not economical.

But now over on GitHub Raziel Einhorn has uploaded plans for his open hardware 1.5 – 3 GHz downconverter which is code named Nigun (Melody). Currently the design has just about been completed, and he is planning to order the first prototype this January. The main component appears to be the ADRF6612 RF mixer which is controlled by an ATSAMD21E18A ARM microcontroller. On the GitHub page he explains the main properties as:

  • Dynamic LO – LO will be determined by the user and programmed by the MCU
  • Almost no filtering – will leave this challenge outside of this project scope
  • Power up and programming via micro-usb connector. Should be able to power up from a USB power-pack (but probably not from a computer port)
  • Highest RF frequency will be 3GHz
  • Product also features a VCO for signal-generation purposes. VCO support should be 200-2700MHz
Nigun Downconverter Schematics
Nigun Downconverter Schematics

HDSDR Version 2.75 (Stable) Released

The beta 2.75 version of HDSDR was released about two months ago. Now the stable version has just been released. HDSDR is a free general purpose SDR receiver, similar in nature to other programs like SDR# and SDR-Console. HDSDR can be downloaded from hdsdr.de.

The author of HDSDR emailed us with the following release information:

this morning we released the final version 2.75. Here’s the changelog:

Version 2.75 (January 01, 2017)
– more recording options
– support for 8bit sampling format – ideal for RTLSDR, halving RF recording size
– display level / clipping for RF and AF
– additive noise generator for hiding aliases
– Highpass Filter for AM/FM deactivatable – useful for slow digimodes
– configurable gain for I/Q output – useful for digimode decoding weak signals of SDRs with >16 Bit dynamic range
– Uniform “Calibration” dialog for Frequency/S-Meter/DC Removal/Channel Skew
– “Custom color palette” to customize colors of Waterfall/Spectrum and some more
– output soundcard no longer necessary (e.g. for recording or monitoring)
– support for 8k display resolution (7680×4320)
– some new keyboard shortcuts (see )
– extended ExtIO capabilities
– experimental transmit capability through ExtIO API interface
– many fixes and improvements

Some of the new features were introduced especially for the RTLSDR Dongles:

– 8 bit support, of course

– displaying the RF (ADC) level in dBFS allow working with deactivated Tuner AGC – NOT oversteering/clipping the ADC.
This would also ease making good suitable recordings as used in
https://www.rtl-sdr.com/using-rpitx-and-an-rtl-sdr-to-reverse-engineer-and-control-ask-devices

Especially for decoding this kind of signals (AM/FM) , deactivating the Highpass filter (Ctrl-H) will make the demodulated Audio clearer:
long periods of positive or negative levels will not fade towards zero.
Find attached recordings and screenshots with active and deactivated highpass filter of a garage door opener demodulated in AM.

– additive noise generator (Ctrl-N) is for hiding some alias carriers in scenarios where the ADC does not see real noise from the antenna.
The noise generators level has to be configured carefully for not hiding real signals. A level between -25 to -10 looked fine for me. But that should be measured in a lab.

Below are the mentioned attached images and .wav files.

Highpass Filter - Active
Highpass Filter – Active
Highpass Filter - Inactive
Highpass Filter – Inactive

Highpass Active .wav file (Download)

Highpass Inactive .wav file (Download)

Receiving the Recently Launched BY70-1 Satellite

BY70-1 is a Chinese amateur Cubesat satellite which was recently launched on December 29, 2016. It is expected to stay in orbit for only 1 – 2 months due to a partial failure with the satellite releasing into an incorrect orbit. The purpose of the satellite is for education in schools and for amateur radio use. The receivable signals include an FM repeater and BPSK telemetry beacon both of which can be received at 436.2 MHz. The telemetry beacon is interesting because it also transmits images from an on board visible light camera. These signals can easily be received with an RTL-SDR or other SDR with an appropriate antenna.

Over on his blog Daneil Estevez has been posting about decoding these telemetry images. He’s been using telemetry data collected by other listeners, and the gr-satellites GNU Radio decoder which is capable of decoding the telemetry beacons on many amateur radio satellites. So far the decoded images haven’t been great, they’re just mostly black with nothing really discernible. Hopefully future decodes will show better images.

If you want to track the satellite and attempt a decode, the Satellite AR Android app has the satellite in its database.

Not many people seem to have gotten telemetry decodes or images yet, but below we show an image decoded by  on Twitter.

BY70-1 Image Decoded by @bg2bhc
BY70-1 Image Decoded by @bg2bhc

Building a Wideband Vivaldi Antenna for SDR Use

Vivaldi’s are linearly polarized broadband antennas that have a directional radiation pattern at higher frequencies. The high end SDR manufacturer RF Space produces their own Vivaldi antennas made from PCB boards which they sell online. The larger the antenna, the lower its receiving frequency, and ones that go down to about 200 MHz are almost the size of a full adult person. But all sizes receive up to 6 GHz maximum. Typically smaller versions of Vivald antennas have been used in the past for L-Band satellite reception.

Over on his blog KD0CQ noted that he always had trouble trying to purchase a Vivaldi from RF Space because they were too popular and always out of stock. So he decided to try and build his own out of PCB boards. On this page he’s collected a bunch of Vivaldi cutout or transfer images. On his second page he shows a Vivaldi antenna that he built out of PCB material, just by using scissors and semi-rigid coax. With the Vivaldi placed outdoors he’s been able to successfully receive and decode L-Band AERO on his Airspy Mini even without an LNA. 

KD0CQ writes that he’ll update his blog soon with more results.

Simple Vivaldi antenna by KD0CQ cut out of PCB board.
Simple Vivaldi antenna by KD0CQ cut out of PCB board.

A Guide to Using RPiTX and an RTL-SDR to Reverse Engineer and Control ASK/OOK Devices

Erhard E. has been experimenting with capturing, analyzing, reverse engineering and then transmitting new ASK/OOK signals with his RTL-SDR and Raspberry Pi running RPiTX. Erhard has written a very informative guide/tutorial (pdf) that explains how he did it for wireless doorbell and for remote control toy cars. RPiTX is software for the Raspberry Pi which allows it to transmit almost any signal via modulation of a GPIO pin. RPiTX related posts have been featured on this blog several times in the past.

First Erhard records a copy of the doorbell signal using his RTL-SDR and then views the waveform in Audacity. He then writes that you’ll need to find the waveform characteristics either manually using Audacity, or by using the rtl_433 decoder. In the tutorial he uses rtl_433 which automatically gives his the pulse width, gap width and pulse period.

Next in order to actually generate the signal using RPiTX he uses the waveform characteristics that he found out and manually creates a .ft hex file that describes the signal to be generated. Then using using the rpitx command, the .ft file can be transmitted.

Later in the tutorial he also shows how he performed the same reverse engineering process with a cheap RC car toy (forward/reverse commands only), which uses OOK encoding on the wireless controller.

The tutorial can be downloaded in PDF form here.

Showing the Pulse Width, Gap Width and Symbol Period of a signal in Audacity.
Showing the Pulse Width, Gap Width and Symbol Period of a signal in Audacity.

Simulating GPS with LimeSDR and Receiving it with an RTL-SDR

In previous posts we showed how Phillip Hahn had been trying to use his RTL-SDR as a GPS receiver on a high powered rocket in order to overcome the COCOM limits which prevent commercial GPS devices from operating when moving faster than 1,900 kmph/1,200 mph and/or higher than 18,000 m/59,000 ft.

In order to test future flights with the RTL-SDR GPS receiver, Phillip has been simulating GPS rocket trajectory signals and using his LimeSDR. The RTL-SDR then receives the simulated GPS signals which are then fed into SoftGNSS for decoding. The simulation simulates the Japanese SS-520-4 rocket which is a 32′ long, 2′ diameter small high powered rocket capable of putting loads like cubesats into orbit affordably. Using the simulated data Phillip is able to calculate the trajectory and see all the motor burns in the velocity profile.

While Phillip intends to use the RTL-SDR on a similar rocket in the future, he notes that the simulation does not take into account problems such as thermal noise, or RF interference, rocket jerk, satellite occlusion and vibration problems.

LimeSDR Simulated GPS Rocket Trajectory Received with RTL-SDR.
LimeSDR Simulated GPS Rocket Trajectory Received with RTL-SDR.

Radio For Everyone new Posts: RTL-SDR Accessories, 5 Easy Mods, FAQ, Legal/Moral Issues and Portable SDR

Akos from the radioforeveryone.com blog (previously sdrformariners/rtlsdrforeveryone) has recently added several new posts. The first new post is a beginners guide to RTL-SDR accessories. In this post he shows and links to his reviews of various RTL-SDR accessory products such as upconverters, baluns, filters, preamps and adapters.

In the second post he shows a guide to 5 easy mods that can be performed on RTL-SDR dongles which will improve their performance. The mods include using a ground plane, using a wire antenna, extending the coax, removing the IR and LED diodes, and putting the dongle into a metal tin.

In the third post he discusses portable software defined radio and shows exactly what products and software you need to set up a an Android or Raspberry Pi based mobile SDR station.

In the remaining new posts Akos has created an RTL-SDR FAQ and a guide to understanding the legal and moral issues of SDR. Finally the last new post we saw is where Akos tests a cooled RTL-SDR V3 vs a stock V3. His results appear to show that the cooled dongle achieves slightly more (avg. 3.73%) position reports.

Akos' guide to RTL-SDR Accessories.
Akos’ guide to RTL-SDR Accessories.

Decapping the R820T and RTL2832U Chips

Over on YouTube the electronupdate channel has posted a video showing the decapping of the R820T and RTL2832U chips. Decapping is the process of removing the plastic packaging on integrated circuit chips, thus exposing the internal circuits printed on the silicon die for viewing. In the video he shows microscope images of each of the decapped chips and explains a bit about what each part of the chip does.

Over on his blog he’s also posted the full decapped images of the R820T and RTL2832U for viewing.

The decapped R820T tuner die.
The decapped R820T tuner die.
SOFTWARE DEFINED RADIO TEARDOWN: R820/RTL2832U DECAP